1. Field of the Invention
The present invention relates to a multilayer chip capacitor and, more particularly, to a circuit board device having a decoupling multilayer chip capacitor capable of allowing a user to personally (directly) adjust an equivalent series resistance (ESR).
2. Description of the Related Art
In general, a multilayer chip capacitor (MLCC) has a structure in which inner electrodes of different polarities are alternately stacked between a plurality of dielectric layers. The MLCC is commonly used as a component of various electronic devices with the advantages that it is small, guarantees a high capacity, and is easily mounted.
In particular, a power supply device for a central processing unit (CPU) of a computer or the like has a problem in that a voltage noise is generated due to a rapid change in a load current in the process of providing a low voltage. Thus, in order to restrain such voltage noise, the MLCC is widely used as a decoupling capacitor for the power supply device.
As the operational frequency increases, the decoupling multilayer chip capacitor needs to have ESR characteristics in order to more stably provide power.
If the ESR value of the multilayer chip capacitor is lower than a required level, an impedance peak at a parallel resonance frequency generated due to an equivalent series inductance (ESL) of a capacitor and a plane capacitance of a microprocessor package increases, while the impedance at a series resonance frequency of the capacitor is excessively lowered. Thus, in order for the user to implement the flat impedance characteristics of a power distributed network, it is desirous to easily adjust the ESR characteristics of the decoupling multilayer capacitor and provide it.
Regarding ESR adjustment, a method of forming outer electrodes and inner electrodes with a material having a high electrical resistance may be considered. In this case, however, if the highly resistant material is used for the outer electrodes, a localized heat spot can be caused by a current concentration phenomenon due to a pin hole. In addition, when the inner electrodes are made of a high resistant material, the material of the inner electrodes must be continuously altered so as to be matched with a ceramic material in line with the high capacity.
Another method for improving ESR is disclosed by U.S. Pat. No. 6,765,781 (Assignee: TDK) in which a linkage electrode is applied to the exterior of a capacity main body to connect inner electrodes in series through the leakage electrode.
However, the above-described ESR adjustment methods are disadvantageous in that they are all executed by the manufacturers. Namely, the electrode structure is modified to be designed and fabricated so as to have a particular desired equivalent series resistance according to the user demands and application products. This problem also arises with the above-mentioned material altering method.
Thus, the related art ESR adjustment methods have difficulty in fabricating individual products that may satisfy various ESR characteristics according to user demand and the conditions of the application products at the capacitor manufacture side. At the capacitor user side, the user must select individual products according to his desired or required ESR conditions.